The present invention relates generally to a method for separation of an ester such as methyl iso-butyrate or methyl methacrylate from a reaction mixture in which the ester is formed by reaction of an organic acid with an alcohol.
In the known industrial method, an ester is generally produced by reacting alcohol with an equimolar amount of organic acid in the presence of a suitable catalyst. The thus produced ester is then purified by fractional distillation. This reaction however suffers from the disadvantage that it is never complete and must be closely controlled in order to avoid formation of by-products. Although the reaction theoretically should be complete, even under ideal conditions, the reaction mixture usually contains a substantial proportion of unreacted alcohol and organic acid which must be separated from the ester. The separation of the ester from the reactants by simple fractional distillation is rendered difficult owing to the formation of alcohol-ester or ester-water azeotropes.
As a result of studies on the separation of esters from the reaction mixture, it has now been found that the ester may be readily separated by reacting an alcohol with an excess amount of organic acid based on that of alcohol, and removing the unreacted alcohol from the reaction mixture as an alcohol-ester azeotrope.